JP2015141213A - Optical scanner and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve heat dissipation performance.SOLUTION: An optical scanner 10 includes a housing 11, a polygon motor 12B, and a sheet metal 18. The housing 11 includes an opening 11G formed in the central part in a sub-scanning direction of a bottom plate 11A. The polygon motor 12B is arranged on the opening 11G in the housing 11, to rotate the polygon mirror 12A. The sheet metal 18 is arranged on an outside surface of the bottom plate 11A, to close the opening 11G, is held by the housing 11 at the edge of the opening 11G, and holds the polygon mirror 12B through the opening 11G. The sheet metal 18 is formed larger than a holding area 19 where the sheet metal is held by the housing 11 at the edge.

Description

  The present invention relates to an optical scanning device that emits a plurality of laser beams from both sides in a sub-scanning direction of a polygon mirror, and an image forming apparatus including the same.

  An electrophotographic image forming apparatus includes an electrostatic latent image carrier, a charging device for charging the surface of the electrostatic latent image carrier to a predetermined potential, and scanning the surface of the electrostatic latent image carrier with laser light. An optical scanning device that forms an electrostatic latent image, a developing device that develops the electrostatic latent image into a toner image, a transfer device that transfers the toner image onto a sheet, and a fixing device that fixes the toner image onto the sheet.

  The optical scanning device includes a light source, a polygon mirror that deflects laser light emitted from the light source, a polygon motor that rotates the polygon mirror, and a housing that houses these.

  Due to the recent demand for higher image formation speed, the rotation speed of polygon mirrors has been increased. When the rotation speed of the polygon mirror is increased, the current flowing through the drive circuit board of the polygon motor increases and the amount of heat generated by the polygon motor increases. Also, the amount of heat generated from the rotating part increases. Furthermore, since the housing is easy to form a structure for attaching a member such as a polygon motor, the housing is often formed of a resin, and the resin has a low thermal conductivity. For these reasons, the temperature inside the housing of the optical scanning device tends to rise.

  In the optical scanning device, in the sub-scanning direction, a polygon mirror and a polygon motor are arranged at the center of the bottom plate of the housing, various lenses and mirrors are arranged on both sides of the polygon mirror, and laser light is emitted from both sides of the polygon mirror. Is a double-sided scanning type optical scanning device. In such a double-sided scanning type optical scanning device, since the casing is thinned, the temperature inside the casing is particularly likely to rise.

  When the temperature inside the case rises, the optical axis angle of the emitted laser beam is shifted due to uneven expansion of various lenses, changes in the mirror angle due to expansion of the case, etc., and problems such as color shift and uneven density Is likely to occur.

  Therefore, a technique for improving heat dissipation by configuring the casing from a plurality of parts and configuring the casing of the part holding the polygon mirror with a resin material having high thermal conductivity is known (for example, (See Patent Document 1).

JP 2007-65378 A

  However, in the prior art, even a resin material having a high thermal conductivity has a poor thermal conductivity compared to a metal, and thus the heat dissipation cannot be made very high.

  An object of the present invention is to provide an optical scanning device capable of improving heat dissipation and an image forming apparatus including the same.

  The optical scanning device of the present invention emits a plurality of laser beams from both sides in the sub-scanning direction of the polygon mirror. The optical scanning device includes a housing, a polygon motor, and a sheet metal. The housing has an opening at the center in the sub-scanning direction of the bottom plate. The polygon motor is disposed on the opening in the casing and rotates the polygon mirror. The sheet metal is disposed on the outer surface of the bottom plate so as to close the opening, is held by the casing at the edge of the opening, and holds the polygon motor through the opening. The sheet metal is configured to be larger than the holding area by the casing at the edge.

  In this configuration, since the polygon motor is held on the sheet metal, the heat generated by the polygon motor is transmitted to the sheet metal by heat conduction. Sheet metal is made of metal and has higher thermal conductivity than resin. In addition, the sheet metal is disposed outside the housing and is configured to be larger than the holding region at the edge of the opening, so that the area that can dissipate heat increases. In addition, since the sheet metal is increased in area and the weight of the bottom portion of the housing is increased, it is possible to reduce the influence of external vibration.

  In the above configuration, the sheet metal preferably extends in one direction.

  In this configuration, the sheet metal is configured to extend along the air blowing direction by a fan for cooling the inside of the image forming apparatus on which the optical scanning device is mounted, thereby forcing the heated air around the sheet metal. Therefore, it is possible to increase the heat dissipation amount per unit time from the sheet metal.

  Further, the sheet metal can be configured such that the end in the width direction in the one direction is bent in a direction away from the bottom plate.

  In this configuration, the sheet metal is configured to extend along the air blowing direction by a fan for cooling the inside of the image forming apparatus on which the optical scanning device is mounted, and the end portion is bent, so that the wind Makes it easier to guide the wind as it flows along the sheet metal. Further, heat can be radiated from the bent end portion, and the heat radiable area can be increased.

  Furthermore, the sheet metal can be configured to exhibit at least a part of a duct shape extending in the one direction.

  In this configuration, the sheet metal is configured to extend along the blowing direction of the fan, and the sheet metal exhibits at least a part of the duct shape, so that the wind can be more easily guided so as to flow along the sheet metal.

  Further, the sheet metal can be configured to exhibit a duct shape extending in one direction.

  In this structure, the standing part of the edge part of the said width direction is connected mutually, and is made into a duct shape, Therefore The air sent in the duct can be reliably sent along a sheet metal to a remote part. For this reason, wind can be applied to a sheet metal in a wider area.

  Furthermore, it is preferable that the sheet metal is also disposed in a light source arrangement region facing a light source that irradiates a polygon mirror with laser light with a bottom plate interposed therebetween.

  In this configuration, heat generated from a light source that is a member having a particularly large calorific value among members other than the polygon motor is also conducted to the sheet metal and radiated from the sheet metal to the air.

  In addition, it is preferable to further include a heat conductive sheet sandwiched between the sheet metal and the bottom plate in the light source arrangement region.

  In this configuration, the heat conduction sheet increases the thermal conductivity from the housing to the sheet metal, so that the heat generated from the light source can be more efficiently conducted to the sheet metal.

  An image forming apparatus according to the present invention includes any one of the optical scanning devices described above.

  In this configuration, heat generated by the polygon motor is transmitted to the sheet metal by heat conduction. By increasing the area of the sheet metal, heat dissipation is improved, and the temperature inside the housing of the optical scanning device can be suppressed. For this reason, the change of the mirror angle by expansion | swelling of various lenses and expansion | swelling of a housing | casing can be suppressed, and problems, such as a color shift and density nonuniformity, can be suppressed.

  According to this invention, heat dissipation can be improved.

1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus including an optical scanning device according to a first embodiment of the present invention. It is the perspective view which looked at the inside of the housing | casing of an optical scanning device from diagonally upward, and has shown the state which removed the upper cover. It is a top view which shows the some optical member of an optical scanning device. It is a front view showing a plurality of optical members of an optical scanning device. It is a perspective view which shows the outer surface of the baseplate of an optical scanning device. It is front sectional drawing of the one part member of an optical scanning device. It is front sectional drawing of the one part member of the optical scanning device concerning 2nd Embodiment. It is front sectional drawing of the one part member of the optical scanning device concerning 3rd Embodiment. It is front sectional drawing of the one part member of the optical scanning device concerning 4th Embodiment. It is side surface sectional drawing of the one part member of the optical scanning device concerning 5th Embodiment.

(First embodiment)
As shown in FIG. 1, the optical scanning device 10 according to the first embodiment of the present invention is mounted on an electrophotographic image forming apparatus 100. The image forming apparatus 100 includes an image reading unit 110, an image forming unit 120, and a paper feeding unit 130.

  The image reading unit 110 reads an image of a document and generates image data.

  In addition to the optical scanning device 10, the image forming unit 120 includes four image forming stations 30A, 30B, 30C, and 30D, an intermediate transfer unit 40, a secondary transfer unit 50, a fixing device 20, and a paper discharge tray 62. Yes.

  The intermediate transfer unit 40 includes an intermediate transfer belt 41, a driving roller 42, and a driven roller 43. The intermediate transfer belt 41 is stretched between the driving roller 42 and the driven roller 43 and moves around the loop path.

  The image forming stations 30 </ b> A to 30 </ b> D are arranged in a line along the intermediate transfer belt 41. The image forming stations 30B to 30D are formed in substantially the same manner as the image forming station 30A.

  The image forming station 30A includes a photosensitive drum 1A, a charger 2A, a developing device 4A, a primary transfer roller 5A, and a cleaning unit 6A. The charger 2A charges the peripheral surface of the photosensitive drum 1A to a predetermined potential. The optical scanning device 10 forms an electrostatic latent image on the peripheral surface of the photosensitive drum 1A by irradiating a laser beam based on the image data. The developing device 4A supplies toner to the peripheral surface of the photosensitive drum 1A to visualize the electrostatic latent image and form a toner image.

  The primary transfer roller 5A is disposed so as to face the respective photosensitive drums 1A of the image forming stations 30A to 30D with the intermediate transfer belt 41 interposed therebetween. Each of the positions where the primary transfer roller 5A and the respective photosensitive drums 1A of the image forming stations 30A to 30D face each other is a primary transfer position. The primary transfer roller 5 </ b> A applies a primary transfer voltage to primarily transfer the toner image formed on the peripheral surface of the photosensitive drum 1 </ b> A to the outer peripheral surface of the intermediate transfer belt 41 at each primary transfer position.

  The black, cyan, magenta, and yellow hue toner images formed on the peripheral surfaces of the respective photosensitive drums 1A, 1B, 1C, and 1D of the image forming stations 30A to 30D are formed on the outer peripheral surface of the intermediate transfer belt 41. Primary transfer is performed so as to overlap, thereby forming a full-color toner image.

  The toner image formed on the outer peripheral surface of the intermediate transfer belt 41 is conveyed to a secondary transfer position where the intermediate transfer belt 41 and the secondary transfer unit 50 face each other as the intermediate transfer belt 41 rotates.

  The paper feed unit 130 includes a paper feed cassette 131 and a manual feed tray 132, and supplies paper one by one from the selected one of the paper feed cassette 131 and the manual feed tray 132 to the paper transport path 61. The paper transport path 61 extends from the paper feed cassette 131 and the manual feed tray 132 to the paper discharge tray 62 via the secondary transfer position and the fixing device 20.

  The secondary transfer unit 50 includes a secondary transfer roller 51. The secondary transfer unit 50 applies a secondary transfer voltage to the secondary transfer roller 51 to secondarily transfer the toner image carried on the outer peripheral surface of the intermediate transfer belt 41 to a sheet.

  The fixing device 20 includes a heating roller 21 and a pressure roller 22 that are in pressure contact with each other. The fixing device 20 firmly and firmly fixes the toner image to the sheet by heating and pressing the sheet conveyed between the heating roller 21 and the pressure roller 22.

  The paper to which the toner image is fixed in the fixing device 20 is discharged to the paper discharge tray 62 with the image surface facing downward.

  As shown in FIGS. 2 to 4, the optical scanning device 10 is a double-sided scanning type that emits a plurality of laser beams from both sides in the sub-scanning direction Y of the polygon mirror 12A. A specific configuration is shown below. The optical scanning device 10 includes a housing 11, a polygon mirror 12A, a polygon motor 12B, two first semiconductor lasers 13A and 13B, two second semiconductor lasers 13C and 13D, a first incident optical system 14A, and a second incident. An optical system 14B, a first imaging optical system 15A, and a second imaging optical system 15B are provided. The first semiconductor lasers 13A and 13B and the second semiconductor lasers 13C and 13D are light sources, respectively.

  The housing 11 is made of resin, and has a rectangular bottom plate 11A, four side plates 11B, 11C, 11D, and 11E surrounding the bottom plate 11A, and an upper lid (not shown).

  A polygon motor 12B is fixed to the center of the bottom plate 11A, and the rotation center of the polygon mirror 12A is connected and fixed to the rotation axis of the polygon motor 12B. The polygon mirror 12A is rotated at a constant angular speed by a polygon motor 12B.

  A drive substrate 11F is fixed to the outside of one side plate 11B of the housing 11. The first semiconductor lasers 13A and 13B and the second semiconductor lasers 13C and 13D are mounted on the drive substrate 11F. The first semiconductor lasers 13A and 13B and the second semiconductor lasers 13C and 13D face the inside of the housing 11 through respective holes formed in the side plate 11B.

  The first semiconductor lasers 13A and 13B and the second semiconductor lasers 13C and 13D are assumed to have a virtual arrangement center line M extending in the main scanning direction X through the rotation center of the polygon mirror 12A. Are arranged symmetrically. A direction orthogonal to the main scanning direction X is defined as a sub-scanning direction Y, and a direction orthogonal to the main scanning direction X and the sub-scanning direction Y (longitudinal direction of the rotation axis of the polygon motor 12B) is defined as a height direction Z.

  The first incident optical system 14A includes two collimator lenses 141A and 142A, two apertures 143A, two mirrors 144A and 145A arranged at the same height as the first semiconductor laser 13A, and a cylindrical lens 16. .

  Similarly, the second incident optical system 14B includes two collimator lenses 141B and 142B, two apertures 143B, two mirrors 144B and 145B arranged at the same height as the second semiconductor laser 13D, and a cylindrical lens. 16 is included.

  The collimator lenses 141A and 142A, the aperture 143A, and the mirrors 144A and 145A of the first incident optical system 14A, and the collimator lenses 141B and 142B, the aperture 143B, and the mirrors 144B and 145B of the second incident optical system 14B are the virtual arrangement centers. They are arranged symmetrically about the line M. The virtual arrangement center line M passes through the center of the cylindrical lens 16, and one half of the cylindrical lens 16 divided by the virtual arrangement center line M is arranged in the first incident optical system 14 </ b> A. Is arranged in the second incident optical system 14B.

  The first incident optical system 14A guides the light beams L1 and L2 of the first semiconductor lasers 13A and 13B to the polygon mirror 12A. The second incident optical system 14B guides the light beams L3 and L4 of the second semiconductor lasers 13C and 13D to the polygon mirror 12A.

  The first imaging optical system 15A includes an fθ lens 151A and four reflecting mirrors 152A, 153A, 154A, 155A. Similarly, the second imaging optical system 15B includes an fθ lens 151B and four reflection mirrors 152B, 153B, 154B, and 155B.

  The fθ lens 151A and the reflection mirrors 152A, 153A, 154A, and 155A of the first imaging optical system 15A, and the fθ lens 151B and the reflection mirrors 152B, 153B, 154B, and 155B of the second imaging optical system 15B are the virtual arrangement center. They are arranged symmetrically about the line M.

  The first imaging optical system 15A guides the light beams L1 and L2 of the first semiconductor lasers 13A and 13B reflected by the polygon mirror 12A to the photosensitive drums 1A and 1B corresponding to black and cyan, respectively. The second imaging optical system 15B guides the light beams L3 and L4 of the second semiconductor lasers 13C and 13D reflected by the polygon mirror 12A to the photosensitive drums 1C and 1D corresponding to magenta and yellow, respectively.

  A BD substrate 17A mounted with a BD mirror 171A and a BD sensor 172A is provided on the first imaging optical system 15A side, and a BD substrate 17B mounted with a BD mirror 171B and a BD sensor 172B also on the second imaging optical system 15B side. Is provided. The BD mirror 171A and the BD sensor 172A on the first imaging optical system 15A side and the BD mirror 171B and the BD sensor 172B on the second imaging optical system 15B side are arranged symmetrically about the virtual arrangement center line M. ing.

  In the optical scanning device 10, a polygon mirror 12A is disposed substantially at the center of the bottom plate 11A of the housing 11, and the first semiconductor lasers 13A and 13B and the first semiconductor lasers 13A and 13B are centered on a virtual arrangement center line M passing through the rotation center of the polygon mirror 12A. The two semiconductor lasers 13C and 13D are arranged symmetrically, the first incident optical system 14A and the second incident optical system 14B are arranged symmetrically, and the first imaging optical system 15A and the second imaging optical system 15B are arranged. They are arranged symmetrically. Therefore, in the side view, the polygon mirror 12A, the first semiconductor lasers 13A and 13B, the second semiconductor lasers 13C and 13D, the first incident optical system 14A, the second incident optical system 14B, and the like are gathered in a small space. The optical scanning device 10 can be downsized.

  As shown in FIGS. 5 and 6, the optical scanning device 10 further includes a metal plate 18 on the outer surface of the bottom plate 11 </ b> A of the housing 11. In FIG. 6, members other than the casing 11, the polygon mirror 12 </ b> A, the polygon motor 12 </ b> B, and the sheet metal 18 are omitted. The same applies to FIGS.

  The housing 11 has an opening 11G at the center in the sub-scanning direction Y of the bottom plate 11A. The polygon motor 12B is disposed on the opening 11G in the housing 11.

  The sheet metal 18 is disposed on the outer surface of the bottom plate 11A so as to close the opening 11G, and holds the polygon motor 12B through the opening 11G. The contact area between the polygon motor 12B and the bottom surface is preferably large.

  The sheet metal 18 is held by the bottom plate 11A at least at the edge of the opening 11G. As an example, the sheet metal 18 is screwed to the bottom plate 11A at the top, bottom, left, and right edges of the opening 11G and the outer edge of the sheet metal 18. Since the sheet metal 18 is held by the bottom plate 11A at the edge of the opening 11G, the backlash of the polygon motor 12B is prevented.

  The sheet metal 18 is configured larger toward the outside of the opening 11G than the holding area 19 which is an area held by screwing or the like at the bottom plate 11A at the edge of the opening 11G.

  Since the polygon motor 12B is held by the sheet metal 18, the heat generated by the polygon motor 12B is transmitted to the sheet metal 18 by heat conduction. The sheet metal 18 is made of metal and has a higher thermal conductivity than the resin. Moreover, since the sheet metal 18 is disposed outside the housing 11 and is configured to be larger than the holding region 19 at the edge of the opening 11G, an area capable of radiating heat is increased. Therefore, according to the optical scanning device 10, the heat dissipation can be improved.

  For this reason, the temperature inside the housing 11 of the optical scanning device 10 can be suppressed. Accordingly, the various lenses such as the collimator lenses 141A, 142A, 141B, 142B, the cylindrical lens 16, and the fθ lenses 151A, 151B are expanded, and the mirrors 144A, 145A, 144B, 145B and the reflecting mirrors 152A, 153A, Changes in the angles of 154A, 155A, 152B, 153B, 154B, and 155B can be suppressed, and problems such as color misregistration and density unevenness can be suppressed.

  Further, since the sheet metal 18 is increased in area and the weight of the bottom portion of the housing 11 is increased, it is possible to make it less susceptible to external vibration.

  In addition, the resin material of the housing 11 in which many optical members are accurately held is not changed to a material having a high thermal conductivity, so that a relatively small design such as an increase in the area of the sheet metal 18 is not required. Heat dissipation can be improved by changing the design.

  The sheet metal 18 is preferably disposed not only in the region facing the polygon motor 12B but also in the light source placement region facing the semiconductor lasers 13A to 13D with the bottom plate 11A interposed therebetween.

  Of the members other than the polygon motor 12B, heat generated from the semiconductor lasers 13A to 13D, which is a member having a particularly large calorific value, is also conducted to the sheet metal 18 and radiated from the sheet metal 18 to the air.

  It is preferable that a heat conduction sheet (not shown) is sandwiched between the metal plate 18 and the bottom plate 11A in the light source arrangement region. Since the thermal conductivity from the bottom plate 11 </ b> A to the metal plate 18 is increased by sandwiching the heat conductive sheet, the heat generated from the semiconductor lasers 13 </ b> A to 13 </ b> D can be more efficiently conducted to the metal plate 18. For this reason, heat dissipation can be improved more.

  The image forming apparatus 100 further includes a fan that is an example of a blower for cooling the inside of the apparatus main body. For example, the fan is disposed at a height near the lower side of the optical scanning device 10 on the back surface of the apparatus main body, and discharges air inside the apparatus main body to the outside. Therefore, in the vicinity of the lower side of the optical scanning device 10, the air is blown from the front side to the back side of the image forming apparatus 100. The direction from the front side to the back side of the image forming apparatus 100 and the main scanning direction X are parallel.

  The sheet metal 18 preferably extends in one direction. In this embodiment, the sheet metal 18 extends from the front side end of the bottom plate 11A to the back side end in the main scanning direction X.

  By configuring the sheet metal 18 so as to extend along the direction of air blow by the fan, the heated air around the sheet metal 18 can be forcibly moved and replaced with air having a relatively low temperature. The amount of heat released per unit time can be increased.

(Second Embodiment)
As shown in FIG. 7, in the optical scanning device 10A according to the second embodiment, the sheet metal 18A has a width direction in a blowing direction by a fan, that is, end portions 181A and 182A in the sub-scanning direction Y in this embodiment are from the bottom plate 11A. It is configured in the same manner as the optical scanning device 10 except that it is bent in the direction of separation. In addition, the same code | symbol is used about the structure similar to the optical scanning device 10. FIG. In addition, the term “bend” here includes a curve.

  The sheet metal 18A is configured to extend along the blowing direction by the fan, and the end portions 181A and 182A are bent, so that the wind can be more easily guided so that the wind flows along the sheet metal 18A. In addition, heat can be radiated from the bent ends 181A and 182A, and the heat radiable area can be increased. Thereby, the heat dissipation is further improved.

(Third embodiment)
As shown in FIG. 8, the optical scanning device 10 </ b> B according to the third embodiment is configured such that the sheet metal 18 </ b> B exhibits a part of a duct shape extending in the air blowing direction by the fan, that is, in the main scanning direction X in this embodiment. The configuration is the same as that of the optical scanning device 10 except for the above. In addition, the same code | symbol is used about the structure similar to the optical scanning device 10. FIG.

  As an example, the sheet metal 18B is configured such that the ends 181B and 182B in the width direction in the blowing direction by the fan, that is, the sub-scanning direction Y in this embodiment, stand up with respect to the bottom plate 11A.

  The sheet metal 18B is configured to extend along the air blowing direction by the fan, and the sheet metal 18B exhibits a part of the duct shape, so that the wind can be more easily guided so that the wind flows along the sheet metal 18B. Thereby, the heat dissipation is further improved.

(Fourth embodiment)
As shown in FIG. 9, the optical scanning device 10 </ b> C according to the fourth embodiment is configured such that the sheet metal 18 </ b> C has a duct shape extending in the fan blowing direction, that is, the main scanning direction X in this embodiment. Except for this, the configuration is the same as that of the optical scanning device 10. In addition, the same code | symbol is used about the structure similar to the optical scanning device 10. FIG.

  The width direction in the air blowing direction by the fan, that is, in this embodiment, the standing portions of the end portions 181C and 182C in the sub-scanning direction Y are connected to each other to form a duct shape, so that the air sent into the duct can be reliably transmitted to the remote portion. Can be blown along the sheet metal 18C. For this reason, wind can be applied to the sheet metal 18C in a wider area.

(Fifth embodiment)
As in the optical scanning device 10D according to the fifth embodiment shown in FIG. 10, the sheet metal 18D is bent in the height direction Z in the process of extending in the blowing direction by the fan, that is, in the direction along the main scanning direction X in this embodiment. It may be. The sheet metal 18D is stably held by the housing 11 by the sheet metal 18D extending along the shape of the bottom plate 11A. Further, the sheet metal 18D is bent, so that the heat radiation area of the sheet metal is increased.

  It is conceivable to construct a new embodiment by combining the technical features of the above-described embodiments.

  The above description of the embodiment is to be considered in all respects as illustrative and not restrictive. The scope of the present invention is shown not by the above embodiments but by the claims. Furthermore, the scope of the present invention is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

10, 10A, 10B, 10C, 10D Optical scanning device 11 Housing 11A Bottom plate 11G Opening 12A Polygon mirror 12B Polygon motor 18, 18A, 18B, 18C, 18D Sheet metal 181A, 182A, 181B, 182B, 181C, 182C End 19 Holding area

Claims (8)

An optical scanning device that emits a plurality of laser beams from both sides in a sub-scanning direction of a polygon mirror,
A housing having an opening in the center of the bottom plate in the sub-scanning direction;
A polygon motor disposed on the opening in the housing and rotating the polygon mirror;
A sheet metal that is disposed on the outer surface of the bottom plate so as to close the opening, is held by the housing at an edge of the opening, and holds the polygon motor through the opening;
The optical scanning device, wherein the sheet metal is configured to be larger than a holding region by the casing at the edge.   The optical scanning device according to claim 1, wherein the sheet metal extends in one direction.   The optical scanning device according to claim 2, wherein the sheet metal is configured such that an end portion in the width direction in the one direction is bent in a direction away from the bottom plate.   The optical scanning device according to claim 2, wherein the sheet metal is configured to exhibit at least a part of a duct shape extending in the one direction.   The optical scanning device according to claim 4, wherein the sheet metal has a duct shape extending in the one direction.   6. The optical scanning device according to claim 1, wherein the sheet metal is also disposed in a light source arrangement region facing the light source that irradiates the polygon mirror with laser light with the bottom plate interposed therebetween.   The optical scanning device according to claim 6, further comprising a heat conductive sheet sandwiched between the sheet metal and the bottom plate in the light source arrangement region.   An image forming apparatus comprising the optical scanning device according to claim 1.

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